For some reason, my Firefox location bar search had changed to Babylon search.
To change it back:
In the addressbar, type “about:config”
The current keyword.URL is a link to Babylon: http://search.babylon.com/?affID=14335&tt=220512_53all&babsrc=KW_ss&mntrId=909d77c400000000000000fff812aab9&q=.
It should be changed back to the default: